Symbatios (Greek: Συμβάτιος, from the ArmenianSmbat), variously also Sabbatios (Σαββάτιος) or Sambates (Σαμβάτης) in some sources,[1] was the eldest son of the Byzantine emperorLeo V the Armenian (r. 813–820). Soon after the coronation of his father, he was crowned co-emperor and renamed Constantine (Κωνσταντίνος). He reigned nominally along with his father until the latter's deposition in 820, after which he was exiled to Prote as a monk.

Symbatios was the eldest son of Leo and his wife, Theodosia. As he was a child at the time of his father's accession, he was born sometime between 800 and 810. The previous emperor, Michael I Rhangabes (r. 811–813), was likely the boy's godfather.[1][2] After Leo deposed Michael I and ascended the throne on Christmas 813, he had the young Symbatios crowned co-emperor and renamed Constantine. The latter name was not chosen randomly: aside from it being a traditional Byzantine imperial name, the assembled troops now publicly acclaimed the emperors "Leo and Constantine", evoking openly the iconoclast emperor Leo III the Isaurian (r. 717–741) and his son Constantine V (r. 741–775). This was a clear statement of intent, not only against external foes like the Bulgars, whom Constantine V had repeatedly defeated, but also in the internal front, presaging Leo's re-adoption of iconoclasm as official state policy.[1][3]

In 815, Constantine nominally presided, as his father's representative, over a Church Council in Constantinople, which reinstated the ban on the veneration of icons.[1][4] After the assassination of his father on 25 December 820, Constantine was banished to the island of Prote along with his mother and three brothers. There, the four brothers were castrated and tonsured. They spent the rest of their days there as monks, although Emperor Michael II the Amorian (r. 820–829) allowed them to keep part of the proceeds from their confiscated estates for their and their servants' upkeep.[5]